Amnion tissue grafts and methods of preparing and using same

ABSTRACT

The invention provides method for preparing amnion tissue grafts, as well as the grafts themselves. In specific embodiments, the tissue graft comprises a single layer of dried amnion from an umbilical cord.

CROSS-REFERENCE TO A RELATED APPLICATION

This application claims the benefit of U.S. provisional application Ser.No. 62/416,528, filed Nov. 2, 2016, which is incorporated herein byreference in its entirety.

BACKGROUND

Tissue grafts are useful for various types of surgical procedures andwound treatments. The tissue used in graft procedures can be collectedfrom humans or from animal specimens. Alternatively, graft tissue can bemanufactured artificially. One source of human tissue, which has beenutilized for decades in surgical procedures, is the placental membrane.

The placenta is an organ that develops during pregnancy to surround thefetus and connect it to the uterine wall. This temporary organ allowsfor transport of gases and nutrients to the fetus, while also providingother metabolic and endocrine functions. The placental membrane consistsof two layers of tissue: amnion, the innermost layer surrounding thedeveloping fetus, and chorion, an outer layer surrounding the amnion andfetus. The amniotic membrane forms an avascular, fluid-filled sac aroundthe fetus, which holds and protects the fetus during development.

In addition to the amniotic sac, another major placental component isthe umbilical cord. This cord-like structure, which attaches a fetus tothe placenta, provides nutrition and support to the developing embryo. Ahuman umbilical cord is typically about 50-60 cm long and 2 cm indiameter. It consists of blood vessels surrounded by a smooth,protective mesenchymal material known as Wharton's jelly, all of whichis contained in a tube formed of amnion.

Amnion tissue grafts are generally used to assist in tissue regenerationand aid in wound healing. Known clinical procedures or applications foramnion grafts include, but are not limited to, ocular reconstruction,burn treatment, gum tissue replacement, and general wound care.

Amnion tissue provides unique grafting characteristics when used forsurgical procedures. Some amnion tissue grafts have the ability toself-adhere or to be fixed in place by, for example, fibrin glue orsuturing.

While using fresh membrane is typically ideal, the limited timeframeavailable for storage of fresh tissue makes such use difficult. Thus,processing methods are needed to facilitate preserving and storingtissue until it is needed for surgical applications. The main goal oftissue processing and preservation is to retain the beneficialcomponents of fresh tissue while achieving a shelf life long enough tolast until surgery. When prepared properly, amnion tissue grafts can bestored for extended periods of time.

BRIEF SUMMARY OF THE INVENTION

The subject invention provides methods for preparing amnion tissuegrafts, as well as the grafts themselves. In specific embodiments, thetissue graft comprises a single membrane of dried amnion from anumbilical cord.

In one embodiment, the method comprises the steps of:

a) making a longitudinal cut in the amnion of an umbilical cord toexpose the contents of the lumen of the umbilical cord;

b) removing blood vessels and Wharton's jelly from the lumen of theumbilical cord to produce a debrided amnion;

c) optionally, incubating the debrided amnion in a holding solution;

d) washing the debrided and, if performed, incubated, amnion in theholding solution;

e) rinsing the washed amnion one or more times in a rinsing solution;and

f) drying the rinsed amnion.

In another embodiment, a partially debrided amnion is obtained andfurther processed by washing, rinsing, and drying and optionally,holding before the washing step.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows Pressure and Temperature charts from drying runs.

DETAILED DISCLOSURE OF THE INVENTION

Amniotic membrane forms the inner lining of the placenta and umbilicalcord during fetal development. The amniotic membrane has three distinctlayers; a single layer of epithelial cells, a thick basement membraneand a non-vascular stromal layer. It contains no HLA antigens or MHCmolecules and is therefore an immunologically privileged material. Theprimary structural component of amniotic membrane is extracellularmatrix consisting of collagens and proteins such as fibronectin,proteoglycans, laminin and glycosaminoglycans. Other molecules found inamniotic membrane include growth factors, metalloproteinases and tissueinhibitors of metalloproteinases, which together with the extracellularmatrix components may play a role in wound healing and cellularingrowth.

The subject invention provides methods for preparing amnion tissuegrafts, as well as the grafts themselves. In specific embodiments, thetissue graft comprises a dried single layer amnion from an umbilicalcord.

In one embodiment, the method comprises the steps of:

a) making a longitudinal cut in the amnion of an umbilical cord toexpose the contents of the lumen of the umbilical cord;

b) removing blood vessels and Wharton's jelly from the lumen of theumbilical cord to produce a debrided amnion;

c) optionally, incubating the debrided amnion in a holding solution;

d) washing the debrided and, if performed, incubated, amnion in theholding solution;

e) rinsing the washed amnion one or more times in a rinsing solution;and

f) drying the rinsed amnion.

In another embodiment, a partially debrided amnion is obtained andfurther processed by washing, rinsing, and drying and optionally,holding before the washing step.

Selected Definitions

“Subject” refers to an animal, such as a mammal, for example a human.The methods described herein can be useful for isolating amnion fromboth humans and non-human animals. In some embodiments, the subject is amammal. The invention can be used in a subject selected fromnon-limiting examples of a human, non-human primate, rat, mouse, pig,horse, cattle, dog or cat.

“Amnion” as used herein refers to amniotic membrane of an umbilicalcord.

“Umbilical cord” refers to a cordlike structure containing blood vesselsthat attaches a fetus to the placenta during gestation. An umbilicalcord comprises a wall of amnion enclosing a lumen comprising, amongother substances, Wharton's jelly and blood vessels.

Producing the Amnion Tissue Graft

In one embodiment, a longitudinal cut in the amnion is made along thefull length of an umbilical cord. The umbilical cord can then be laidout flat in approximately rectangular shape with amnion at the bottomand the contents of the lumen over the amnion. The luminal contents ofthe umbilical cord can be removed from the amnion in a process referredto as “debriding” the amnion. The process of debriding comprisesseparating the contents of the umbilical cord from the amnion usingappropriate tools, for example, surgical tools such as forceps,scissors, and the like.

The purpose of the debriding step is to remove all or substantially allof the luminal contents. Wharton's jelly is an amorphous gel-like mass;it may not be possible, or desireable, to remove 100% of the Wharton'sjelly. Accordingly, for the purposes of the invention, “removingWharton's jelly from the luminal contents of the umbilical cord” meansthat more than about 50%, 70%,80%, 90%, 95%, and even more than 99%, ofthe Wharton's jelly from the lumen of an umbilical cord is separatedfrom the amnion. Therefore, some Wharton's jelly may be left in thedebrided amnion.

In one embodiment, an amount of Wharton's jelly remains thatsubstantially or completely fills valleys between ridges that wouldotherwise exist in the amnion tissue.

In one embodiment, the debridement step is performed in a rinsingsolution. In one embodiment, the rinsing solution is phosphate bufferedsaline comprising:

-   -   1) NaCl: 7 to 11 g/L; preferably, 8-10 g/L; more preferably,        about 9 g/L;    -   2) Anhydrous Na₂HPO₄: 0.2 to 1.5 g/L; preferably, about 0.5 to 1        g/L; more preferably, about 0.8 g/L; and    -   3) KH₂PO₄: 0.1 to 0.2 g/L; preferably, about 0.15 g/L.

At pH: 7 to 8.8; preferably about 7.4.

In a particular embodiment, the rinsing solution comprises about 9 g/LNaCl, about 0.8 g/L anhydrous Na₂HPO₄, about 0.14 g/L KH₂PO₄, at a pH ofabout 7.4.

In certain embodiments, the rinsing solution does not contain calcium ormagnesium.

In one embodiment, the debrided amnion is stored in a holding solutionfor a holding period. The holding period can be about two to five hours,particularly, about two, three, four or five hours. The holding step canbe performed at a temperature of between 20° C. to 30° C., preferably,at about 25° C.

In one embodiment, the holding solution comprises:

-   -   1) Tween-20: 0.4% to 0.6% (v/v); preferably about 0.5% (v/v);    -   2) An antimicrobial compound: For example, polyaminopropyl        biguanide (also called, polyhexamethylene biguanide        hydrochloride or PHMB) at 0.04% to 0.06% (w/v), preferably about        0.05% (w/v). In another embodiment, the antimicrobial compound        is chlorhexidine gluconate at a concentration of, for example        0.01% to 1.5% and, more preferably, from 0.03% to 0.08%.        Additional antimicrobial compounds, for example, antibiotics or        antifungal agents and their appropriate concentrations are known        to a person of ordinary skill in the art and such embodiments        are within the purview of the invention;    -   3) NaCl: 7 to 10 g/L; preferably, 8-9 g/L; more preferably,        about 9 g/L; and    -   4) An appropriate buffer, at pH 6.0 to 8.0, preferably, 6.5 to        7.0; preferably, about 6.6 to 6.8; and more preferably, 6.7±0.1.        An example of a buffer that can be used in the holding solution        is Bis-Tris Propane buffer, 8 to 12 mM; preferably, 9 to 11 mM;        more preferably, about 10 mM. Additional examples of buffers        include MES, Bis-Tris, ADA, ACES, PIPES, MOPSO, BES, MOPS, TES,        HEPES, DIPSO, MOBS, TAPSO, HEPPSO, POPSO, EPPS (HEPPS), Tricine,        Gly-Gly, Bicine, HEPBS, TAPS, AMPD, TABS, AMPSO, CHES, CAPSO,        AMP, CAPS, and CAPS.

In a particular embodiment, the holding solution comprises about 0.5%(v/v) Tween-20; about 9 g/L NaCl; about 0.05% (w/v) PHMB; and about 10mM Bis-Tris Propane buffer at pH of 6.7±0.1.

In one embodiment, the debrided amnion, with or without the holdingstep, is stored at about 4° C. for about 10 to 15 hours before a washingstep. The step of storing debrided amnion at 4° C. can be performed inthe holding solution.

In another embodiment, the debrided amnion, either with or without theholding step, is washed in a washing step. Preferably, the washing stepcomprises agitating the debrided amnion in the holding solution.

Agitation during the washing step can be performed, for example, on ashaker for about two to five hours, particularly, for about two, three,four, or five hours. Agitation can be performed at about 50 to 300rotations per minute (RPM), preferably at about 100 to 200 RPM, morepreferably at about 125 to 175 RPM, even more preferably, at about 150RPM.

In one embodiment, a debrided amnion is stored in a holding solution inthe holding step and the washing step is performed in the same holdingsolution by transferring the amnion to a shaker.

After the washing step, the washed amnion is rinsed in a rinsing step.The rinsing step is performed in the rinsing solution, described above.In a particular embodiment, the rinsing solution used in the rinsingstep comprises about 9 g/L NaCl, about 0.8 g/L anhydrous Na₂HPO₄, andabout 0.14 g/L KH₂PO₄, at a pH of about 7.4.

In one embodiment, the step of rinsing is performed three to five timesin a rinsing solution. Each rinsing step can be performed for about 5 to30 minutes; preferably, for about 10 to 25 minutes; and even morepreferably, for about 15 minutes.

The rinsing step can be performed on a shaker at about 50 to 300 RPM,preferably at about 100 to 200 RPM, more preferably at about 125 to 175RPM, even more preferably, at about 150 RPM.

The step of rinsing is designed to remove components of the washingsolution from the graft as well as remaining blood or debris from thedebriding step.

In one embodiment, the rinsed amnion is dried. The step of drying can beperformed for about 5 to 25 hours, preferably, for about 10 to 20 hours,and even more preferably, for about 15 hours. In one embodiment, dryingis performed at a pressure lower than the atmospheric pressure, forexample, at a pressure of between about 15 mBar to 60 mBar. In a typicaldrying process under reduced pressure, a pressure of about 40 to 60mBar, preferably, between 45 to 55 mBar, more preferably, about 50 mBaris used at the beginning of the drying step. The pressure can changeover time during the step of drying as shown in FIG. 1. The pressure atthe end of the drying process of about 12 to 16 hours can be, forexample, about 10 to 15 mBar.

In a specific embodiment, the step of drying is performed for about 15hours at a temperature of between 30° C. and 40° C. and under initialpressure of between about 50 mBar, which reduces to a pressure of about15 mBar towards the end of the drying step.

A further embodiment of the invention provides a method for preparing adried amnion membrane from umbilical cord, the method comprising thesteps of:

a) obtaining a partially-debrided amnion;

b) removing, blood vessels and Wharton's jelly to produce a debridedamnion;

c) optionally, incubating the debrided amnion in a holding solution;

d) washing the debrided and, if performed, incubated, amnion in theholding solution;

e) rinsing the washed amnion one or more times in a rinsing solution;and

f) drying the washed amnion.

The partially-debrided amnion can be obtained in a frozen state, inwhich case, the frozen partially-debrided amnion is thawed beforefurther processing. Thawing can be performed over about 6 to 20 hours,preferably over about 8 to 15 hours, and more preferably, over about 10to 12 hours. Thawing can be performed at a temperature of between 20° C.to 30° C., preferably, between 22° C. to 28° C., even more preferably,at about 24° C. to 25° C.

The steps of removing the blood vessels and the Wharton's jelly toproduce a debrided amnion, incubating the debrided amnion in a holdingsolution, washing the debrided and if performed, incubated, amnion inthe holding solution, rinsing the washed amnion one or more times in therinsing solution, and drying the rinsed amnion are described above andsuch description is applicable to the embodiment of the invention wherea partially debrided amnion is the starting materials.

Amnion Tissue Grafts

The umbilical cord/amnion tissue grafts produced according to thesubject invention may be, for example, ½ cm to 4 cm wide and, forexample, 2 to 6 cm long.

In one embodiment the graft is provided with an indicium of which sideis from the outside of the umbilical cord and which side is ftom theinside of the umbilical cord. In one embodiment, the indicium is a tabprovided at a specified corner of the graft. As used herein, referenceto a “tab” means a protrusion out from the edge of the graft. Theprotrusion may be, for example, in the shape of a rectangle, square ortriangle. In one embodiment, to place the graft endothelial side up, thetab is in the upper left corner. When used in practice, the tab alsohelps a user to grasp the tissue graft with a tool, for example, aforceps. Tabs are also useful in repositioning the tissue graft at asurgical site, for example, a user can maneuver the tissue graft at thesurgical site by grasping the tissue graft with a tool, for example, aforceps, and repositioning the tissue graft as desired.

The tissue grafts prepared according to the subject invention areprocessed such as they have less than 20% water content. Preferably, thewater content is about 12% to about 18%. In preferred embodiments, thewater content is 15% or less.

The graft preferably contains no blood vessels, or chorion tissue. Thatis, the graft consists, or consists essentially of, amnion tissue,typically including some Wharton's jelly.

When dried (e.g., after processing), the tissue graft has a thickness ofabout 150 μm to 250 μm, preferably about 175 μm to 225 μm. As notedabove, the tissue grafts comprise an amount of Wharton's Jelly thatmakes the surface smooth (e.g., few, if any, ridges). Preferably, thegraft has uniform thickness, varying by less than 20%, 15%, 10%, 5%, 2%,or even 1% across its surface.

The tissue graft can be sterilized with e-beam irradiation of about, forexample, less than 25 KGy and, preferably, about 15-19 KGy.

The tissue grafts comprise no live cells, glycerol or ice crystals.

In one embodiment, the graft is treated with, for example, ascorbic acidto improve its whiteness.

In one embodiment, the graft is coated, or infused, with anantimicrobial composition that persists with the graft so as to reduceand/or prevent infections once the graft is implanted. The antimicrobialcomposition may be, for example, polyhexanide (polyhexamethylenebiguanide, PHMB) or chlorhexidine gluconate (CHG) (or other saltthereof) in an amount such that microbes are exposed to about 0.01% toabout 1.0% CHG and preferably about 0.02% to about 0.08%. Mostpreferably to concentration of CHG is about 0.03% to 0.05%. The graftmay comprise other substances including, but not limited to, growthfactors, anti-inflammatory agents, and stem cells. The amnion tissuegrafts produced according to the methods described herein show similarlevels of bioactive compounds as present in the amnion used to producethe tissue graft. Such bioactive compounds include interleukins, tissueinhibitors of metalloproteinases, epidermal growth factor, fibroblastgrowth factor, platelet derived growth factor, vascular endothelialgrowth factor, and transforming growth factor present before and afterprocessing. These bioactive compounds facilitate healing when the tissuegrafts of the invention are placed are used in surgical procedures.

Advantageously, the amnion tissue grafts of the subject invention havesufficient strength to be sutured. The suture may be, for example, asize 7-0, 8-0, or even 9-0 USP size or smaller suture, whichadvantageously does not tear through the graft.

The tissue graft may be packaged inside a first foil package that issterile inside and out and placed within the sterile inside of a secondpackage.

Use of the Amnion Tissue Graft

The amnion tissue grafts can be used, for example, to assist in tissueregeneration and aid in wound healing. Exemplary clinical procedures orapplications for the subject amnion grafts include, but are not limitedto, tendon repair, dural defects, intra-abominable adhesions, peritonealreconstructions, genital reconstruction, ocular reconstruction, burntreatment, gum tissue replacement, nerve repair, promote healing atsurgical sites, and general acute and chronic wound care.

The tissue graft may be placed directly at the surgical site orrehydrated prior to placement. If rehydration is desired, roomtemperature sterile saline or sterile Lactated Ringer's solution (LRS)can be used for rehydration.

When placed at a surgical site, either as dry or after rehydration, thetissue grafts of the invention drape and conform to the tissue or organon which they are placed. Thus, the tissue grafts can self-adhere to thetissue or organ on which they are placed. Adherence of the tissue graftsto a tissue or an organ can be facilitated by suturing the tissue graftto the site. The self-adherence property of the tissue grafts of theinvention can be enhanced by designing the tissue grafts to have roundedcorners. Rounding of the corners facilitate placement of the tissuegrafts at a site in the body because the rounded corners conform to thetarget site more easily than sharp corners, for example, right angledcorners. Although the tissue graft conforms and adheres to the tissue ororgan, the tissue grafts have sufficient strength to be repositioned bya user, for example, a surgeon, without breaking or disintegrating.

When implanted the tissue graft remains in place for 8, 10, 12, 16 ormore weeks. Advantageously, the tissue grafts of the subject inventioncan be used to help prevent or reduce scar tissue by favorably modifyingthe host immune response via, for example, a barrier function at thesite of the injury.

As used herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. Furthermore, to the extent that the terms “including,”“includes,” “having,” “has,” “with,” or variants thereof are used ineither the detailed description and/or the claims, such terms areintended to be inclusive in a manner similar to the term “comprising”.

The term “about” or “approximately” means within an acceptable errorrange for the particular value as determined by one of ordinary skill inthe art, which will depend in part on how the value is measured ordetermined, i.e., the limitations of the measurement system. Forexample, “about” can mean within 1 or more than 1 standard deviation,per the practice in the art. Alternatively, “about” can mean a range ofup to 0-20%, 0 to 10%, 0 to 5%, or up to 1% of a given value.Alternatively, particularly with respect to biological systems orprocesses, the term can mean within an order of magnitude, preferablywithin 5-fold, and more preferably within 2-fold, of a value. Whereparticular values are described in the application and claims, unlessotherwise stated the term “about” meaning within an acceptable errorrange for the particular value should be assumed. In the context ofcompositions containing amounts of ingredients where the terms “about”or “approximately” are used, these compositions contain the statedamount of the ingredient with a variation (error range) of 0-10% aroundthe value (X±10%).

In the present disclosure, ranges are stated in shorthand to avoidhaving to set out at length and describe each and every value within therange. Any appropriate value within the range can be selected, whereappropriate, as the upper value, lower value, or the terminus of therange. For example, a range of 0.1-1.0 represents the terminal values of0.1 and 1.0, as well as the intermediate values of 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9, and all intermediate ranges encompassed within0.1-1.0, such as 0.2-0.5, 0.2-0.8, 0.7-1.0, etc. Values having at leasttwo significant digits within a range are envisioned, for example, arange of 5-10 indicates all the values between 5.0 and 10.0 as well asbetween 5.00 and 10.00 including the terminal values.

All patents, patent applications, provisional applications, andpublications referred to or cited herein are incorporated by referencein their entirety, including all figures and tables, to the extent theyare not inconsistent with the explicit teachings of this specification.

Following are examples which illustrate procedures for practicing theinvention. These examples should not be construed as limiting. Allpercentages are by weight and all solvent mixture proportions are byvolume unless otherwise noted.

EXAMPLE 1 Bench-Top Execution of a Human Umbilical Cord MembraneProcessing

This Example provides a procedure for extraction of materials from thetissue and retention of process residuals in the tissue.

The aqueous processing time used in this Example was intended tomaximize the potential for extracting materials, such as growth factorsor components of the extracellular matrix, from the tissue beforetesting. Using milder processing conditions less extraction occurs.

Additionally, the use of tissue that was prepared after recovery andbefore freezing by having the cord cut open and bulk tissue removed fromthe stromal face, maximizes the surface area for diffusion of materialsout of the tissue during the recovery process and the thawing beforedebridement. Reducing times and volumes for the rinse series between thedetergent wash and the drying process increases the potential forretention of processing agents and so maximizes the risk of affectingbiocompatibility.

Equipment:

1. Shaker incubator

2. Biosafety cabinets

3. Vacuum drying oven

4. Vacuum Sealer

5. Balance

6. Push gauge

7. Refrigerator

Debridement

Tissue was obtained in the frozen state with significant debridementalready conducted. This “pre-debridement” removed bulk tissue andvariable amounts of the blood vessels. Thawing the frozen tissue wasconducted at ambient temperature (˜24° C.) overnight. Average thaw timewas 15:21 hr with a range of 14:34 to 17:03 hrs.

Debridement involved cutting open and removing any remaining bloodvessels with forceps. Bulk tissue (principally Wharton's Jelly) was thenremoved with curved iris scissors until all tissue above the plane ofthe tissue that could be gripped firmly between Adson forceps (e.g.,tissue “ridges” that can be gripped without also gripping the membraneitself) was removed.

The average cord length was 44.5 cm (32 to 68 cm range). Debridementproduced a wet tissue membrane that was about 1300±300 microns thickwith a range of 510 to 1900 microns.

The unprocessed tissue membranes were collected immediately afterdebridement and after measurements were made, the membranes were storedin sterile conical tubes in a refrigerator until the drying step.

Processed samples were also collected immediately after debridement andthen measured but were then processed with the remainder of the cordbefore drying.

Processing

Table 1 below shows the durations and set-points of the process run inthis Example. n=3 for the three processing runs except where noted whenthe step references individual donors.

TABLE 1 Processing parameters Avg. value Min Max Pre-rinse (Step 1b)Duration (n = 12) 1:47 1:01 2:48 Volume of Sol. F (L) 2 +/− 0.05 NA NATemperature (° C.) 28 NA NA (set-point) RPM's (set-point) 150 NA NAProst-Debridement hold (Step 2) Duration (hr) 3:00 3:00 3:02 Volume ofSol. H (L) 2 +/− 0.05 NA NA Room Temperature, No Yes NA NA agitationWash (Step 3) Solution was not changed between the holding and thewashing step, i.e., the solution used in the holding step is used whileshaking in the washing step. Duration (hr) 3:33 3:30 3:38 Temperature (°C.) 30.0 NA NA (set-point) RPM's (set-point) 150 NA NA Rinse #1 (Step 4)Duration (min) 10 10 11 Volume of Sol F (L) 1.5 +/−0.05 NA NATemperature (° C.) 22.0 NA NA (set-point) RPM's (set-point) 130 NA NARinse #2 (Step 5) Duration (min) 10 10 10 Volume of Sol F (L) 1.5 +/−0.05 NA NA Temperature (° C.) 22.0 NA NA (set-point) RPM's (set-point)130 NA NA Rinse #3 (Step 6) Duration (min) 10 10 10 Volume of Sol. F (L)1.5 +/− 0.05 NA NA Temperature (° C.) 22.0 NA NA (set-point) RPM's(set-point) 130 NA NA Rinse #4 (Step 7) Duration (min) 11 10 13 Volumeof Sol. F (L) 1.5 +/− 0.05 NA NA Temperature (° C.) 22.0 NA NA(set-point) RPM's (set-point) 130 NA NA Drying (Step 8) Duration, hr(start to 15.4   15.4   15.5 door open)Solution F is rinsing solution and Solution H is holding solution.

Drying

Drying was performed as described below.

TABLE 2 Drying program used (from Table 2 of protocol) TemperaturePressure (° C.) (mBar) Drying step (Start)/(Finish) (Start)/(Finish)Time (hr) Step 1 Ambient/35 Ambient/35 NA. till conditions met (startstep) Step 2 35/35 35/15 1 min (note pressure will not be reached) Step3 35/35 15/15 15 Total time ~15   hrs Time weighted 35 ° C.(approximate, timed steps only) average temperature Time weighted 15mBar (approximate, timed steps only) average pressure

The drying procedure dried the tissue at about 30° C. to 40° C.,preferably, about 33° C. to 37° C., even more preferably about, 34° C.to 36° C., and particularly, about 35° C. The drying step is performedin a medium vacuum. The final vacuum pressure (absolute) can be about 10to 20 mBar, preferably, about 12 to 18 mBar, even more preferably, about14 to 16 mBar, and particularly, about 15 mBar. However, the vacuumpressure at any time during the drying process is related to the watercontent of the tissue.

The drying time was 15-16 hours (note that the actual time may vary asthe 1st step continues until pressure and temperature are met and willvary based on initial conditions). For example, in one embodiment, therequired temperature and pressure are reached within about 1 to 10minutes, in about 2 to 5 minutes, or in about 2 to 3 minutes.

The pressure and temperature profiles of three development runs areshown in FIG. 1.

In all three runs, the chamber was at approximately 15 mBar by 730minutes after the start of the run. Condensation was observed on theinside of the front window of the chamber in approximately the sametimeframe as the pressure increase observed at about 50 minutes into therun. A “shoulder” is observed in the pressure plot between 30 and 25mBar which might represent the end of primary drying (i.e. removal ofwater not bound to other molecules). The chamber temperature varied lessthan 0.5° C. from the set-point through the run after the set-point wasreached.

To reduce the possibility of absorbing moisture from the atmosphere, thedrying assemblies still in the drying bag were placed in poly bags andsealed with a zip tie until used (if sizing and packaging was notstarted immediately). The processed and unprocessed samples showed anaverage loss of mass on drying of 95% (Table 3).

TABLE 3 Wet and dry weights of tissue samples Run #1 Run #2 Run #3 Lot#1 Lot #2 Lot #3 Lot #4 Lot #1 Lot #2 Lot #3 Lot #4 Lot #1 Lot #2 Lot #3Lot #4 Wet weight, g 1.121 1.81 1.434 1.522 1.394 1.479 1.71 1.673 1.3922.399 1.433 1.662 (unprocessed sample) Dry weight, g 0.077 0.09 0.0750.078 0.054 0.077 0.099 0.091 0.079 0.112 0.082 0.081 (unprocessedsample) Wet weight, g 1.047 1.399 1.547 1.445 1.285 1.92 2.288 1.7190.85 1.401 1.574 1.855 (processed sample) Dry weight, g 0.053 0.0690.058 0.163 0.058 0.099 0.089 0.091 0.045 0.06 0.084 0.069 (processedsample) % decrease in 93.1% 95.0% 94.8% 94.9% 96.1% 94.8% 94.2% 94.6%94.3% 95.3% 94.3% 95.1% Unprocessed weight % decrease in 94.9% 95.1%96.3% 88.7% 95.5% 94.8% 96.1% 94.7% 94.7% 95.7% 94.7% 96.3% Processedweight Avg % decrease in Unprocessed 94.7% SD 0.7% Avg % decrease inweight, all 94.8% SD 1.5% weight samples Avg % decrease in Processed94.8% SD 2.0% weight Weights from scale result in significant figures.Percentages are shown at 3 significant figures.

Appearance and Final Sizing

Samples were manually sized using a scalpel and ruler. Lots with samplesintended for bioburden testing were sized first using an autoclavedcutting board. Subsequent Lots within each Run were sized using adisposable cutting board with a pre-printed cm scale grid. Thisdisposable cutting board was not steam sterilizable, but was cleanedwith 70% isopropyl alcohol and air-dried prior to use.

Tissue Thicknesses

Accounting for the significant digits of the measurement, wet tissueafter debridement was 1300±300 microns in thickness and dry tissue was200±60 microns in thickness. The observed range for wet tissue (24samples; 64 measurements) was 510 to 1900 microns. The observed rangefor dry tissue (24 samples; 72 measurements) was 50 to 300 microns.

TABLE 5 Tissue thicknesses Run #3 Run #1 Run #2 Lot Lot #1 Lot #2 Lot #3Lot #4 Lot #1 Lot #2 Lot #3 Lot #4 Lot #1 Lot #2 Lot #3 #4 Wet 42 51 4275 45 36 35 52 48  28 51  64 thickness, 43 53 62 63 60 32 33 26 64  6046  55 Thous NA NA NA NA 56 47 64 57 22  57 54  46 (unprocessed sample)Dry thickness,  9  5  5 10  3  4  7 10  7  10  7  6 Thous  9  4  6  5  3 4  9  2  5   6  6  6 (unprocessed 12  8  4  9  3  5  4  9  5  11  6  4sample) Wet 47 50 55 63 46 35 63 38 20  59 52  53 thickness, 50 50 60 5456 44 73 63 44  43 66  48 Thous NA NA NA NA 55 42 54 64 49  37 53  40(processed sample) Dry thickness,  8  7  7 10  5  8  4  9  6   4  5  7Thous  6 12  5  7  7  7  5 11  5   4  6  5 (processed  6 12 12  6  6  8 7 11  5   7  6  4 sample) Average Wet thickness, Unprocessed sample inThousandths of inch: 49 SD 13 in 1245 SD 323 microns Average Wetthickness, Processed sample in Thousandths of inch: 51 SD 11 in 1291 SD271 microns Overall Average Wet thickness in Thousandths of inch: 50 SD12 in 1268 SD 297 microns Average Dry thickness, Unprocessed sample inThousandths of inch:  6 SD  3 in  161 SD  65 microns Average Drythickness, Processed sample in Thousandths of inch:  7 SD  2 in  176 SD 60 microns Overall Average Dry thickness in Thousandths of inch:  7 SD 2 in  169 SD  63 microns Gauge used, an analogue dial gauge, showedeither 2 or 3 significant figures as read. This table shows the micronconversion to one micron. SD: Standard Deviation, Thous: Thousandth ofan inch

TABLE 6 Aqueous Process Conditions Tested (this protocol) AgitationAlternative Process setpoint Temperature Volume Agitation TemperatureVolume Process Step Time (rpm) setpoint (° C.) Solution (L) Time (rpm)(° C.) Solution (L) Step 1, Perform as rapidly as possible in Biosafetystorage minimal Perform as rapidly as possible in storage NA,Debridement Cabinet solution volume to Biosafety Cabinet solutionminimal (0.9% keep tissue (0.9% volume to saline) wet saline) keeptissue wet Step 1b, Post- 1:47 hr 150 28 F   2 ± 0.05 Step not inalternative process debridement (1:01- incubation 2:48) (each donorenters at a different time) Step 2, Post- 3:00 hr  0 ambient (held H   2± 0.05 0-2.5 0 ambient H 1.95 ± 0.05 debridement (3:00- in hood) hr hold3:02) Step 3, Process 3:33 hr 150 30 H No 1-1.5 140 ± 5 26 ± 2 H No Wash(3:30- solution hr solution 3:38) change change Step 4, Process 10 min130 22 F 1.5 ± 0.05 15-40 140 ± 5 26 ± 2 F 1.95 ± 0.05 Rinse #1 (10-11)min Step 5, Process 10 min 130 22 F 1.5 ± 0.05 15-40 140 ± 5 26 ± 2 F1.95 ± 0.05 Rinse #2 (10-10) min Step 6, Process 10 min 130 22 F 1.5 ±0.05 15-40 140 ± 5 26 ± 2 F 1.95 ± 0.05 Rinse #3 (10-10) min Step 7,Process 11 min 130 22 F 1.5 ± 0.05 15-40 140 ± 5 26 ± 2 F 1.95 ± 0.05Rinse #4 (10-13) min Total aqueous 7:15 hr (7:12-7:21) 2:00 to 6:40process time not including time of changes not including time of changes

TABLE 7 Drying Process Conditions This Example Pressure Temperature(mBar) Alternative Process (° C.) (Start)/ Temperature (° C.) Pressure(mBar) Drying step (Start)/(Finish) (Finish) Time (hr) (Start)/(Finish)(Start)/(Finish) Time (hr) Step 1 (start Ambient/35 Ambient/35 Tillconditions met Ambient/35 Ambient/35 Till conditions met step) Step 235/35 35/15 1 min (note pressure will 35/35 35/15 1 min (note pressurenot be reached) will not be reached) Step 3 35/35 15/15 15 35/35 15/1516 Step 4 NA Shut off heating element (set to 20° C.) and vent chamberwith nitrogen then shut down system. This holds the tissue in an inertenvironment (~1 atm of nitrogen and approximately ambient temperature)until the chamber is opened. Total time (start 15.4 hr (15.4-15.5) ~16.5hrs to door open or nitrogen purge)

CONCLUSIONS

Tissue thawing was conducted at ambient temperature (˜24°) overnight,14-18 hrs. Debridement resulted in a wet membrane of about 1.3 mmthickness, which was reduced after drying to about 0.2 mm. The weightloss on drying observed was about 95% for all samples. Table 6summarizes the aqueous processing conditions tested and potentialconditions for an alternative process. The potential alternative processconditions are selected to be overall milder processing conditions forthe tissue (principally less total contact time) while providing greaterpotential to remove residual processing agents (increased time,agitation, and temperature in Steps 3-7).

Table 7 summarizes the drying processing conditions tested and potentialconditions for an alternative process. The potential alternative processconditions are selected ensure that the drying observed is at least asrobust as that observed in this protocol.

Alternative solutions to the nitrogen purge as a terminal hold step arepossible, such as shutting the heating element off and maintainingvacuum. The samples made under this protocol are appropriate forcharacterization testing.

1. A method for preparing a dried amnion tissue graft from an umbilical cord, the method comprising the steps of: making a longitudinal cut in amnion of an umbilical cord that has a lumen in order to expose contents of the lumen; removing, from the contents of the lumen, blood vessels and Wharton's jelly to produce a debrided amnion; washing the debrided amnion in a holding solution; rinsing the washed amnion one or more times in a rinsing solution; and drying the rinsed amnion.
 2. The method of claim 1, further comprising: incubating the debrided amnion in the holding solution before washing the debrided amnion in the holding solution.
 3. The method of claim 1, wherein the holding solution comprises: Tween-20: about 0.4% to about 0.6% (v/v), an antimicrobial compound, NaCl: about 7 to about 10 g/L, and a buffer at pH of about 6.5 to about 7.0.
 4. (canceled)
 5. (canceled)
 6. The method of claim 1, wherein the step of washing is conducted for about three hours and comprises agitation performed at about 100 to about 200 rotations per minute.
 7. The method of claim 1, wherein the rinsing solution has a pH of about 7.4 and comprises: NaCl: about 7 to about 10 g/L, anhydrous Na₂HPO₄: about 0.5 to about 1.5 g/L, and KH₂PO₄: about 0.1 to about 0.2 g/L.
 8. (canceled)
 9. The method of claim 1, wherein the step of rinsing is performed for three to five times in the rinsing solution and each rinsing step is performed at about 100 rotations per minute to about 200 rotations per minute.
 10. (canceled)
 11. The method of claim 1, wherein the debrided amnion is stored at about 4° C. before the washing step.
 12. The method of claim 1, wherein the step of drying is performed under pressure at a temperature of between about 30° C. and about 40° C.
 13. A method for obtaining a dried amnion membrane from umbilical cord, the method comprising the steps of: obtaining a partially-debrided amnion; removing, blood vessels and Wharton's jelly to produce a debrided amnion; washing the debrided amnion in a holding solution; rinsing the washed amnion one or more times in a rinsing solution; and drying the rinsed amnion.
 14. The method of claim 13, wherein the partially-debrided amnion is obtained in a frozen state and the method further comprises thawing the frozen partially-debrided amnion.
 15. The method of claim 13, further comprising: incubating the debrided amnion in the holding solution before washing the debrided amnion in the holding solution.
 16. The method of claim 13, wherein the holding solution comprises: Tween-20: about 0.4% to about 0.6% (v/v), an antimicrobial compound, NaCl: about 7 to about 10 g/L, and a buffer at pH of about 6.5 to about 7.0.
 17. (canceled)
 18. (canceled)
 19. The method of claim 13, wherein the step of washing is conducted for about three hours and comprises agitation performed at about 100 rotations per minute to about 200 rotations per minute.
 20. The method of claim 13, wherein the rinsing solution has a solution of about 7.4 and comprises: NaCl: about 7 to about 10 g/L, anhydrous Na₂HPO₄: about 0.5 to about 1.5 g/L, and KH₂PO₄: about 0.1 to about 0.2 g/L.
 21. (canceled)
 22. The method of claim 13, wherein the step of rinsing is performed for three to five times in a rinsing solution and wherein each rinsing step is performed at about 100 rotations per minute to about 200 rotations per minute.
 23. (canceled)
 24. The method of claim 13, wherein the debrided amnion is stored at about 4° C. before the washing step.
 25. The method of claim 13, wherein the step of drying is performed under pressure at a temperature of between about 30° C. and about 40° C.
 26. (canceled)
 27. An amnion tissue graft comprising: a single membrane of umbilical cord amnion, wherein a smooth surface is created by Wharton's jelly and wherein the amnion tissue graft comprises less than about 20% water and a thickness of about 150 μm to about 250 μm.
 28. The amnion tissue graft, according to claim 27, that does not comprise glycerol.
 29. (canceled)
 30. (canceled)
 31. The amnion tissue graft, according to claim 27, wherein the thickness does not vary by more than 20%.
 32. The amnion tissue graft, according to claim 27, comprising an indicium that distinguishes epithelial side of the tissue graft from the stromal side of the tissue graft.
 33. The amnion tissue graft, according to claim 32, wherein the indicium is a protrusion out from a specified area of the graft.
 34. (canceled)
 35. The amnion tissue graft, according to claim 33, wherein the protrusion is designed to be suitable for being grasped by a forceps.
 36. (canceled)
 37. The amnion tissue graft, according to claim 27, further comprising one of more bioactive compounds, wherein the one or more bioactive compounds include one or more of: interleukins, tissue inhibitors of metalloproteinases, epidermal growth factor, fibroblast growth factor, platelet derived growth factor, vascular endothelial growth factor, and transforming growth factor.
 38. The amnion tissue graft, according to claim 27, wherein the tissue graft, when placed on a tissue or an organ, conforms and adheres to the tissue or organ.
 39. The amnion tissue graft, according to claim 38, wherein the tissue graft, after conforming and adhering to the tissue or organ, does not disintegrate or break if repositioned by a user.
 40. The amnion tissue graft, according to claim 27, wherein the tissue graft, when placed on the tissue or the organ, remains in place for at least 8 weeks.
 41. (canceled) 